1. Field of the Invention
The present invention is related to an outer rotor structure for an ac fan and more particularly to an outer rotor structure adapted to be combined with metal blades for convenient assembly.
2. Description of the Related Art
Referring to FIG. 1, a conventional ac fan includes an outer rotor 9. The outer rotor 9 generally consists of a plurality of annular pole plates 90, which are stacked on each other. The stacked pole plates 90 are combined with a rotor hub 91. A plurality of blades 92 are equi-spaced and welded on an outer circumference of the outer rotor 9.
In order to rotate the outer rotor 9 in a balanced manner, the conventional blades 92 must be equi-spaced precisely around an outer periphery of the outer rotor 9. Thereby, it can be seen that a need remains for recision instruments, such as a clamp, for finding out precise welding points of the blades 92 positioned on the outer circumference of the outer rotor 9. In attempting to determine these welding points, assembly/manufacturing operations are sophisticated and time-wasting. Moreover, in an initial welding operation, no fixing support exists between any two welding points of the blades 92 and therefore a unilateral force biases the first welding of one of the blades 92. The blade 92 is relatively shifted on the outer rotor 9. Consequently, the combined blade and outer rotor member is unsymmetrical in structure and unbalanced in rotation so that the unsymmetrical blades cause vibration and noise.
The present invention intends to provide an outer rotor structure for an ac fan adapted to combine with metal blades in such a way to mitigate and overcome the above problem.
The primary objective of this invention is to provide an outer rotor structure for an ac fan adapted to combine with metal blades for convenient assembling and manufacture.
The secondary objective of this invention is to provide the outer rotor structure for the ac fan having assembling grooves to mount metal blades at predetermined positions and angles, thereby rotating the rotor in a stable and balanced manner.
The outer rotor structure for the ac fan in accordance with the present invention mainly comprises a plurality of annular pole plates used to stack on each other to form an outer rotor. Each of the pole plates includes an axial hole, a plurality of poles, at least one aligning member and a plurality of recessions. The aligning member is used to align the two adjacent pole plates for stacking so that the recessions of the pole plate are turned at a slight angle in stacked relationship with those of the adjacent pole plate. The longitudinally connected recessions are formed as a plurality of assembling grooves adapted to mount ends of metal blades therein at predetermined positions by welding.
Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description and the accompanying drawings.